CN101375422B - Device and method for converting thermal energy into electrical energy - Google Patents

Abstract

A current source and method of producing the current source are provided. The current source includes a metal source, a buffer layer, a filter and a collector. An electrical connection is provided to the metal layer and semiconductor layer and a magnetic field applier may be also provided. The source metal has localized states at a bottom of the conduction band and probability amplification. The interaction of the various layers produces a spontaneous current. The movement of charge across the current source produces a voltage, which rises until a balancing reverse current appears. If a load is connected to the current source, current flows through the load and power is dissipated. The energy for this comes from the thermal energy in the current source, and the device gets cooler.

Description

Device and method for converting thermal energy into electrical energy

priority

This application claims priority to US Provisional Patent Application 60/750,575, filed December 14, 2005, which is hereby incorporated by reference in its entirety.

technical field

The present invention relates to current sources. More specifically, the present invention relates to current sources comprising metals, semiconductors and insulators.

Background technique

There are multiple energy bands in solids. These energy bands include valence and conduction bands. The conduction band is at a higher energy than the valence band. Each energy band contains multiple energy states that charge carriers (electrons or holes) may be in. In semiconductors and insulators, the conduction band is separated from the valence band by a band gap. There are essentially no energy states in the band gap.

In semiconductors and insulators at zero temperature and not under excitation conditions, the energy states in the valence band are completely occupied by electrons, while the energy states in the conduction band are completely occupied by holes, i.e. without electrons. In metals, on the other hand, the conduction and valence bands are the same. Thus, metals are highly conductive since electrons are essentially free to migrate from occupied to unoccupied energy states. Ideally, on the other hand, in an insulator or undoped semiconductor, the conductivity is lower because the electrons completely occupy the valence band, so there are no energy states to which electrons can move. However, limited conductivity also exists in insulators or undoped semiconductors due to thermal excitation. Some electrons in the valence band receive enough energy to transition across the band gap. Once the electrons are in the conduction band, they can conduct current, as can the gaps left in the valence band. As the bandgap increases, the conductivity decreases exponentially. Thus, in metals the bandgap is zero due to the conduction band overlapping the valence band, whereas in insulators the bandgap is greater than 4eV (e.g. 8.0eV for _SiO2 ) and in semiconductors it is between zero and 4eV.

Energy bands are represented in terms of momentum space. That is, the energy bands of a solid are expressed in terms of the relationship between possible states in energy and possible states in momentum. Other structures are also used to characterize solids. For example, in solid-state physics, the Fermi surface is often used to describe aspects of solids. The Fermi surface is an abstract boundary or interface used to characterize and predict the thermal, electrical, magnetic and optical properties of metals, semimetals and semiconductors. The Fermi surface is related to the periodicity of the lattices that form crystalline solids (that is, the distances between the individual elements that form the lattices), and to the occupancy of electronic energy bands in these materials. The Fermi surface defines a constant energy surface in momentum space. At absolute zero, the Fermi surface separates the partial from the full state. The electrical properties of a material are determined by the shape of the Fermi surface, since electric currents are induced by changes in the occupancy of energy states near the Fermi surface.

Many electronic and other devices use metals, insulators and semiconductors. One example of such a device includes a current source. A current source is a device that supplies a substantially constant amount of current independent of the voltage across its terminals. An ideal current source generates a voltage to maintain a specified current. Many electronic devices use current configurations that include current sources.

Description of drawings

The present invention is illustrated by way of example without limitation in the accompanying drawings, in which like reference numerals refer to similar elements.

Figure 1 illustrates one embodiment of a current source.

Figures 2a, 2b and 2c show energy band diagrams for electronic transitions in an embodiment of the source in Figure 1 .

Fig. 3a and Fig. 3b are the graphs of the variation of the excitation rate with the temperature and the variation of the minimum detection temperature with the Ni composition in the embodiment of the source in Fig. 1, respectively.

Figures 4a, 4b and 4c are graphs of L as a function of temperature for W, Pd and Ni, respectively, in an embodiment of the source of Figure 1 .

Figures 5a and 5b illustrate the energy band diagrams of the sources and different buffers in the embodiment of Figure 1 .

Figures 6a, 6b and 6c show energy band diagrams for embodiments of different current sources.

Figures 7a, 7b and 7c show the energy band diagrams of embodiments of different current sources together with related equivalent circuit diagrams and current-voltage curve diagrams.

Figure 8 shows an energy band diagram of the filter-collector region of an embodiment of a current source.

Figure 9 shows an energy band diagram of the source-buffer-filter region of an embodiment of a current source.

Skilled artisans will appreciate that elements shown in the figures are for simplicity and clarity and have not necessarily been drawn to scale.

Detailed ways

The invention provides a current source and a method of making the current source. The current source includes at least a metal layer and a semiconductor layer. Electrical connections are provided to the metal layer and the semiconductor layer, and a magnetic field applicator may be provided. The interaction between these layers creates a spontaneous electrical current. The movement of charge across the current source creates a voltage that rises until a balancing reverse current occurs. If a load is connected to a current source, current flows through the load and power is dissipated. The energy used comes from thermal energy in the current source, and the device cools down.

Referring to FIG. 1 , in one embodiment, a current source 100 includes four layers 102 , 104 , 106 and 108 . The four layers include source 102 , buffer 104 , filter 106 and collector 108 . Each of the four layers contacts at least one other layer; that is, the source 102 contacts the buffer 104 , the buffer 104 contacts the filter 106 , and the filter contacts the collector 108 . Lead 110 is electrically connected to source 102 and collector 108 from which current can be drawn. Magnetic field B may be applied in a direction substantially perpendicular to layers 102 , 104 , 106 , and 108 by magnetic source 120 , such as a coil.

Although layers 102, 104, 106, and 108 are each shown as a single layer, one or more of these layers 102, 104, 106, and 108 may be multiple layers. The interaction of source 102, buffer 104, filter 106 and collector 108 produces a spontaneous current. The movement of charges across the current source 100 creates a voltage that rises until a balancing reverse current occurs. If the load 112 is connected to the current source 100 through the leads 110, current flows through the load 112 and dissipates power. The energy used comes from thermal energy 100 in the current source, and the current source 100 cools down.

Source 102 is a metal or metal mixture with localized energy states at the bottom of the conduction band. FIG. 2 a schematically shows a localized energy state 204 at the bottom of the conduction band 202 . Interactions between electrons near the Fermi surface and localized electrons trapped on the localized energy state 202 occasionally raise the localized electrons to the Fermi surface, as shown by transition 1 in FIG. 2b. The energy used for this transition is between about 1 and 6 eV and comes from the energy of localized electrons colliding with multiple free electrons. Normal collisions return electrons to localized energy states and create excess electrons above the Fermi surface and excess holes below, as shown with transition 2 in Figure 2b and in Figure 2c. These energetic electrons and holes can be the source of electrical current. The interaction between localized electrons and phonons may also raise localized electrons to the Fermi level. In this case, the energy for the transition comes from multiple phonons.

Suitable source metals have at least two properties. First, the source has localized energy states at the bottom of its conduction band. These energy states should have a lower energy E than at the bottom of the conduction band, about 0.01 eV < E < about 0.05 eV. The number of these energy states should be small enough so that their overlap is small. That is, the number of energy states should be small enough that the levels are not degenerate (ie, they do not extend into impurity bands that merge with the conduction band). In one embodiment, the concentration is less than about 1000 ppm (parts per million). Second, the probability of transition 1 shown in Fig. 2b occurring in the source should be large enough to generate enough high-energy electrons. Localized energy states in metals can be generated in three ways: disorder in the metal, small amounts of impurities, or an applied magnetic field (as shown in Figure 1).

Disordered metals can be divided into two categories: pure metals and mixtures. Atoms of transition metals and rare earth metals have partially filled d-shells. Transition metals are elements characterized by filling of inner d-electron orbitals (or shells) with increasing atomic number. Transition metals include elements with atomic numbers 21 to 30, 39 to 48, 58 to 80, and 89 to 112, especially those from titanium to copper and below them on the International Union of Pure and Applied Chemistry (IUPAC) periodic table elements in the columns of .

Transition metals have randomly oriented magnetic moments due to incomplete filling of the d-shell. The random orientation of the magnetic moments of these shells can create a disordered potential in these metals for conducting electrons. In particular, the potential experienced by conduction electrons on an atom can depend on the relative orientation of the magnetic moment of the atom to its nearest neighbor. Most transition metals have a crystal structure with each atom having 12 closest neighbors. Most of the remaining transition metals have structures with 8 nearest neighbor atoms. For an atom with a sufficiently low potential to produce a local energy state with E > about 0.01 eV below the bottom of the conduction band, it may be that 9 of its closest neighbors have a magnetic moment aligned with its magnetic moment, 3 with its The magnetic moments are anti-aligned. With randomly aligned magnetic moments, the fraction of atoms with localized energy states can be low enough to satisfy the conditions listed above.

The normal condition is more complicated because most d-shells have more than two possible orientations (j > 1/2, where j is the quantum number of angular momentum), but the same principle applies. In the ferromagnetic materials Fe, Co and Ni, for T<T _c (Curie temperature), the relative orientation of adjacent magnetic moments is not random. At T=0, all magnetic moments are aligned, and there is no probability of atoms having lower than average potentials. As the temperature increases, the disorder increases. At a certain temperature To, some atoms may have localized energy states. As the temperature increases further, the number of localized energy states increases.

In a mixture of two or more metals, the random placement of different atoms can create a disordered potential. The mixture may consist of metals that are normally miscible (eg Ni-Cu, Pd-Ag, Pt-Au) or metals that are not normally mixed but can be deposited in a mixed state. Examples of normally immiscible metals include Fe-Co and Ti-V.

Moving from disordered metals to metals containing impurities, some impurities in some metals can create localized energy states. For non-transition metals (such as those in columns 2 and 13-17 in the new IUPAC notation), the impurity metal should be in the same column of the periodic table as the parent metal, and usually lower in that column. For example, Ga or In may be used as an impurity in Al, or K or Rb may be used as an impurity in Na. However, there are exceptions to these rules; for example, Bi impurities in Pb produce localized energy states. For transition metals, the impurity metal can be in the same column as the parent metal, or in a column to the right of the parent metal's column. Cu impurities in Ni are one such example.

The concentration of impurity atoms can range from less than 1 ppm up to an upper limit where isolated localized energy states overlap and merge into disordered localized energy states. For low concentrations (<1000 ppm - 1000 parts per million), the number of energetic electrons generated is proportional to the concentration of the impurity.

In addition to providing impurities, an external magnetic field can also be applied to generate a current source. If a magnetic field is applied to the metal, energy states localized in two dimensions (called Landau states) are created at the bottom of the conduction band. In order to generate Landau energy states, metals are essentially free of disorder. For example, the purity of non-transition metals should be greater than about 99.9% (eg, less than 10 ppm). As shown in FIG. 1 , a magnetic field B is applied generally perpendicular to the surface of source 102 .

Normally, the excitation of electrons from localized energy states at the bottom of the conduction band to the Fermi surface occurs very infrequently. The frequency with which such events occur can be increased by a process hereinafter referred to as "probability amplification". Probability amplification can occur in transition metals through interactions between incomplete d-shells of neighboring atoms and thermal vibrations (phonons) of the atomic lattice. In non-transition metals, by applying an alternating electric field and a non-parallel magnetic field B, probability amplification can be generated near (eg, within about 100 Angstroms of) the physical surface of the metal.

In a given metal, probability amplification values can be assigned to electrons in individual energy bands and to phonons. For example, a transition metal with S and D bands has probability amplification values PAS (S band), PAD (D band), and PAL (phonon). In many metals, the intrinsic probability amplification of electrons is greater than the externally generated probability amplification, making the probability amplification substantially independent of external factors such as applied magnetic field, applied electric field, temperature, and pressure. For metals with one conduction band, the value of probability amplification for electrons varies inversely with the ease with which electrons move from atom to atom. S electrons move the easiest, so PAS is smaller. P electrons are less mobile, so PAP (probability amplification in P band) is larger. The ease with which D electrons move is much less, so the PAD is much larger. F electrons in rare earth metals move so hard that they don't form energy bands at all, so these rules don't apply to them.

The same trend applies between metals. In the group of Cr, Mo, and W, d electrons are easy to move, so PAD is small. The further to the right in the periodic table, the d electrons become more and more inactive, and the PAD increases until the Ni, Pd, Pt group with the largest PAD. The same changes in the columns as well. The d-shells of atoms in column 5 tend to be deeper than atoms in column 4 or 6. So, eg PAD is larger in Pd than in Ni or Pt. For metals with more than one conduction band, interactions between electrons in different shells of an atom can affect the probability amplification of the energy bands. In transition metals, PAS is larger than in non-transition metals (but still much smaller than PAD) because of the interaction between the s-shell and the d-shell. PAS will be largest in those transition metals with the largest PAD.

The probability amplification PAL of electrons and phonons can be influenced by external factors. As mentioned above, one way that PAL can be obtained close to the physical surface (eg, within about 100 Angstroms) is by applying an alternating electric field as well as a magnetic field. Electric and magnetic fields are not parallel to each other.

One way to apply the electric field is to have the adjacent layer or layers (i.e. buffer layer 104 or filter layer 106) be of a material that has a high density of optically active localized phonon modes . In this way, the material has a large number of vibrating charged atoms, creating an alternating electric field. This alternating electric field is able to penetrate a short distance into the source 102 . Typical vibrational frequencies of charged atoms extend to between about 10 ¹² and 10 ¹³ Hz. Copper, for example, has a skin depth of 200 Angstroms for a vibrational frequency of about 10 ¹³ Hz. For other metals, this depth can be different.

A magnetic field can be applied externally. In various embodiments, the magnetic field can be applied by placing the current source 100 in the solenoid 120 (as shown in FIG. 1 ) or by placing a permanent magnet nearby. The output of source 102 can then be controlled by varying the strength of the applied magnetic field.

In addition, probability amplification increases with temperature. At low temperatures, the number of excitations dn/dt per unit time and unit volume is below the detectable limit, as shown in Fig. 3a. At a finite turn on temperature T _o , dn/dt becomes detectable and rises rapidly with temperature. The value of T _o for a given metal is determined by the nature of the localized energy states and the availability of probability amplification. The T _o value of a mixture can be varied continuously over a predetermined range by varying the components of a particular mixture. For example, in a Cu-Ni alloy, the disorder is greatest in the vicinity of 50% Cu-50% Ni. Only Ni atoms have incomplete d-shells, so the probability amplification increases with Ni content. For this series of alloys, the plot _of T as a function of composition is expected to have the shape shown in Fig. 3b.

The thickness of the source 102 can vary from a few atoms thick (approximately 10 Angstroms) to the maximum thickness desired for the entire current source 100 . For thicknesses below about 100 Angstroms, buffers may be used on one or both sides of the source 102 .

Due to the disorder and probability amplification of transition metals, they can all be regarded as alternative source metals. Many of the transition metals have turn-on temperatures T _o that are too high to be practical. For some metals, the upper bound on the turn-on temperature can be estimated using thermal conductivity, resistivity and thermopower data over a range of temperatures. The Lorentz number L is defined by formula (1):

L=(k*r)/T+S ² (1)

In formula (1), k is the thermal conductivity, r is the resistivity, and S is the thermoelectric potential of the metal. L should be close to the size of 2.443x10 ^-8 watt-ohm/(°C) ² at high temperature. The seven metals with significant deviations are Mo, W, Ni, Pd, Pt, Fe and Co. Table 1, Tables 2a and 2b, Table 3 and Figures 4a, 4b and 4c show the data for Pd, W and Ni. ΔK in the table is the amount of additional thermal conductivity to achieve the measured L in addition to the thermal conductivity due to the conduction electrons present in the metal. ΔK can be calculated by formula (1) using the measured k, r and S. If this additional thermal conductivity comes from that of the lattice (the only conventional possibility), its value should be proportional to 1/T for temperatures above the Debye temperature of the metal. Any portion of ΔK that is not attributable to lattice thermal conductivity (especially ΔK that increases with temperature) can be a sign of thermal conductivity from excitation of electrons from localized energy states—meaning that in metals There are localized energy states and probability amplification. However, although these seven metals make good source metals, the data on L versus T alone cannot preclude the use of metals. Excitation of localized energy states does not always affect thermal and electrical conductivity. Mixtures of metals can be studied in the same way. Cu-Ni, Ag-Pd and Au-Pt alloys can be good source materials.

Table 1 Palladium (Pd)

Table 2a Tungsten (W)

Table 2b Tungsten

T1 T2 ΔK(T1)/ΔK(r2) ΔK(T1)/ΔK(T2) theory 400 600 1.47 1.50 600 800 1.29 1.33 800 1000 1.13 1.25 1000 1200 1.10 1.20 1200 1400 1.02 1.17

Table 3 Nickel (Ni)

T(K) Thermal conductivity(watts/cm*deg) Resistivity (ohm-cm)*10⁶ Thermoelectric potential (microvolts/deg) L+S²(x10³) ΔK(watts/cm*deg C) 100 1.64 .986 -8.50 1.62 0.21 150 1.22 2.237 -10.98 1.83 0.11 200 1.07 3.703 -13.45 2.00 0.07 250 .975 5.384 -16.55 2.13 0.06 300 .907 7.237 -19.52 2.23 0.05 400 .802 11.814 -23.99 2..43 0.07 500 .722 17.704 -25.75 2.62 0.10 600 .656 25.554 -22.16 2.84 0.13 1000 .718 41.496 -29.85 3.07 0.15 1200 .762 46.728 -35.42 3.09 0.167

The tables show three cases. For Pd, ΔK increases monotonically with T from 100K to 1200K. Estimates of To are difficult, but 200K is a solid upper bound. For Ni, ΔK decreases with T at low temperatures, reaches a minimum at 300K, and increases with T for T > 300K. The upper boundary of 300K is a safe upper boundary. This is consistent with our understanding of the disordered nature of Ni. Nickel is ferromagnetic below 620K. In OK, all local magnetic moments are aligned, so there is no disorder due to it. As the temperature increases, more and more of the magnetic moments are misaligned, until at 620K they all point in random directions. At temperatures between OK and 620K there will be just the right amount of disorder, large enough to have excitations and small enough to have large localized energy states. Fe and Co show the same behavior, T _o (Fe) about 370K and T _o (Co) about 500K. A small amount of impurities in these three ferromagnetic metals can lower their Curie temperature, which also lowers T _o . For W, ΔK never increases with temperature, but for two different temperatures (as shown in Table 2b), the ratio of ΔK differs from that expected for pure lattice conductivity, rather than the temperature-invariant local The excitation of localized energy states is consistent with the additional contribution to thermal conductivity. It is difficult to estimate To, but there appears to be excitation at T=800K. Note that these estimates of T _o for metals are made for the interior of these metals, and the values of T _o near the surface may be different due to the different degree of probability amplification near the surface.

Among the transition metals, seven metals that may be the best candidates for source metals are Mo, W, Ni, Pd, Pt, Fe, and Co. The L versus T data for each of these metals indicates the presence of excitation. Transition metals that are in the same column as one of these metals but whose L as a function of T data do not show evidence of excitation may also hold promise. These metals include Cr, Ru, Rh, Os and Ir. The rest of the transition metals are probably poor candidates compared to those already mentioned.

Source metals with isolated impurity atoms have been discussed. If the host metal is a transition metal, probability amplification may be intrinsic to that metal. Probability amplification can be provided from outside the metal if the host metal is a non-transition metal without disorder-producing impurities. If localized energy states are generated by a magnetic field, metals are essentially free of disorder without an applied magnetic field. In this case, any pure non-transition metal such as Al or Sn can be used. Magnetic fields that generate Landau energy states can be used for probability amplification.

Turning to buffer 104 , buffer 104 allows the excitation process in source 102 to occur close enough to the surface of source 102 that a significant fraction of the excess electrons and excess holes away from the Fermi energy reaches the surface of source 102 . For this to happen, the bottom of the conduction band in source 102 where the localized energy states are located is aligned with the forbidden band of buffer 104 . Suitable buffers 104 may be metals, insulators or semiconductors. Buffer 104 should be thin enough (approximately 10-50 Angstroms) to allow high energy charges (electrons or holes) to pass through mostly to filter 106 . For example, if buffer 104 is an insulator, charge from source 102 can tunnel through buffer 104 to filter 106 .

Figures 5a and 5b illustrate two situations. Figure 5a illustrates an energy band diagram for a material that is unsuitable as a buffer for a particular source. As shown in Figure 5a, the localized energy states and the bottom of the conduction band in the source 102 are aligned with the conduction band of the buffer 104, while the tops of the conduction bands of the source 102 and buffer 104 are offset by an energy _ΔE1 . The presence of the material forming buffer 104 disrupts the conditions for excitation in source 102 to occur close to the interface. In this case, as shown in the attached graph, the number of energetic electrons increases with the distance from the interface. As shown in Figure 5b, the localized energy states and the bottom of the conduction band in the source 102 are shifted by an energy _ΔE2 , and the tops of the conduction bands of the source 102 and buffer 104 are aligned. If the energy bands of the filter 106 are properly aligned with the source 102, the buffer 104 can be eliminated and thus the filter 106 can act as a buffer. In this case, as shown in the figure, the number of energetic electrons does not vary with the distance from the interface.

Turning to the filter 106, the filter 106 serves to conduct the high energy charges originating from the source 102 and block the flow of electrons close to the Fermi surface. In one embodiment, the filter 106 comprises a semiconductor, such as an elemental semiconductor such as Si or Ge, or a compound semiconductor such as a III-V semiconductor. Alternatively, filter 106 may comprise an insulator such as _SiO2 , CaO, or AlN. In various embodiments, filter 106 may conduct energetic electrons and/or holes while blocking other charge carriers. For example, in one embodiment, filter 106 conducts energetic electrons and blocks all other charges. In another embodiment, the filter 106 conducts high energy holes and blocks all other charges. In another embodiment, both high energy electrons and high energy holes are transported through the filter 106 . In the last case above, the output current polarity of current source 100 is determined by the predominant charge carriers. These embodiments will be described in detail below with reference to FIG. 6 .

Collector 108 can be a metal or a heavily doped semiconductor (eg, 10 ¹⁷ cm ⁻³ or higher dopants), and can have any thickness greater than about 10 Angstroms. If external electrical connections are made to the collector 108, it should be at least 1 micron thicker. The collector 108 may be selected to form an ohmic contact with the semiconductor filter 106 in some cases and a rectifying contact in other cases. As shown in FIG. 8, the surface energy state pinning of the Fermi level greatly determines the size of the potential barrier between the metal and the semiconductor. In this case an ohmic contact can be formed between the filter 106 and the collector 108 by heavily doping the collector side of the filter 106 . As shown in Figure 9, the semiconductor on the side of the buffer layer can be lightly doped to form a rectifying contact at the buffer-filter interface. The choice of collector metal in this case can be based on compatibility with adjacent layers. For example Sn can be a good choice.

If the filter 106 is a II-VI semiconductor or other semiconductor that does not have a surface energy state clamp, the relationship between the semiconductor and the metal can be determined by the relative positions of the Fermi level of the metal and the conduction band and valence band edges of the semiconductor. the nature of the contact. For example, Pd and Pt form rectifying contacts with ZnO. Sn and Al form ohmic contacts with ZnO.

Excitation processes in the source metal cause more electrons and holes to move away from the Fermi energy than would be predicted by equilibrium statistical mechanics. Buffer 104 allows these high energy charges to reach the surface of source 102 and enter and pass through buffer 104 into filter 106 . Filter 106 allows some of the high energy charges to penetrate into collector 108 . Since the collector 108 is a common metal, there is no excess high energy charge that can pass through the filter 106 . Consequently, charge builds up at collector 108 and an electric field develops in filter 106 . The electric field increases to develop balanced currents flowing in opposite directions. If the electric field is increased too much, a breakdown can occur in the semiconductor, destroying its filtering ability.

Additionally, filter 106 and collector 108 allow sufficient reverse current flow so that breakdown does not occur. This can be accomplished in a number of ways. Tunneling from collector 108 to buffer 104 or source 102 may occur if the semiconductor is thin enough (about 50 Angstroms). If the semiconductor has enough defects (such as amorphous silicon or germanium), conduction through defect energy states in the middle of the forbidden band can occur. If the collector metal forms an ohmic contact with the filter layer semiconductor, a Schottky diode is formed. As charge builds up in the collector, the Schottky diode becomes forward biased in the collector-source direction and develops a balanced reverse current.

If the semiconductor in filter 106 is undoped, it is inherently high resistance, and the thickness of filter 106 is limited to about 100 to 200 angstroms to prevent space charge effects that may introduce instability to the output current. If the semiconductor is doped or has low resistance, the thickness can be greater than about 100 Angstroms.

Possible semiconductors include Si, Ge, GaAs, AlAs, AlSb, _SnO2 , etc. Insulators that can be used include MgO and CaO. If the semiconductor also provides probability amplification as previously described, it has a large number of localized phonon modes. Mixture semiconductors include, for example, _{AlxGa1 -xAs} or _{AlAsxSb1 -x} or _{ZnOxS1 -x} , where x can vary from about 0.25 to 0.75. These mixtures are good semiconductors, but have disordered phonon spectra with many localized modes. These modes provide an alternating electric field which, when combined with an externally applied magnetic field, provides probability amplification in the source. More complex semiconductors, such as organic semiconductors, can also be used.

As previously described, current source 100 includes a series of thin layers 102, 104, 106, and 108 of metals and semiconductors and/or insulators. These layers 102, 104, 106 and 108 can be produced by vacuum deposition such that they are in contact with each other. Different vacuum deposition techniques may be suitable for manufacturing the current source 100 . These vacuum deposition techniques include sputtering, chemical vapor deposition, and electron beam evaporation.

Deposition takes place in a vacuum chamber. The chamber includes a container capable of maintaining a vacuum. The chamber also has an electrical feedthrough, which enables electrical current to be fed to wires in the chamber, and a motion feedthrough connected to a vacuum pump through vacuum lines and valves, which enables movement of the target within the container. The vacuum chamber maintains a vacuum of less than about 10 ⁻⁶ torr during the deposition process. The material to be evaporated is placed in a conical basket, eg made of tungsten wire. If the material to be evaporated is in the form of a thin wire or foil, it can simply be wrapped around a tungsten wire. One end of the tungsten wire is connected to the electrical feedthrough, while the other end of the tungsten wire is connected to the wall of the container, which is used for electrical grounding. If an external voltage is applied to the electrical feedthrough, current flows through the tungsten wire, heating the tungsten wire and the material in contact with it. Passing a sufficient current, the material is heated enough to vaporize. Since it is in a vacuum, atoms are emitted substantially uniformly in all directions. The target material is placed on a carrier connected to the motion feedthrough so that it can be moved to the optimal position to receive the evaporated material. To a good approximation, since the material evaporates substantially uniformly in all directions, the amount of impingement on the target, and thus the thickness of the resulting layer, can be given by a simple geometric relationship with respect to the amount of material in the basket and the distance from the basket to the target understanding to calculate. When deposition of one layer is complete, the target is moved to a new location, current is passed through another basket holding material for the next layer and the process is repeated. The individual layers are thereby produced without generating large amounts of impurities at the interface. Care should be taken when selecting the material used to adjoin the layers, as the deposited material may not coat the target uniformly but instead form islands on top of the target, especially for layers that are too thin.

An example device includes a steel substrate on which a series of layers are formed. These layers may include 1000 angstroms of Sn, 100 angstroms of Ge, 30 angstroms of Pb, and 1000 angstroms of Pd. The 30 Angstrom layer of Pb forms the buffer. This series can be repeated as many times as necessary. After repeating this series the desired number of times, a final layer of 1 micron of Sn is deposited. If the vacuum is broken to reload the material, it can be done after the Pd deposition. This introduces a thin layer (approximately 20 angstroms) of PdO between the Pd and the subsequent Sn layer. The 1000 Angstrom layer of Sn forms the collector layer, the Ge forms the filter, the 30 Angstrom layer of Pb forms the buffer, and the Pd forms the source.

The steel substrate can be a conventional steel backing with a diameter of about 1 cm. The steel substrate is cleaned, rinsed with distilled water, and dried eg with nitrogen. The steel backing may also be polished to a suitable brightness with a soft cotton cloth. A single layer, such as Sn, can be deposited. If this layer is removable with an adhesive (eg Scotch tape), the substrate is cleaned again.

After suitable cleaning, the sheet is placed on a carrier and the deposited material is placed in a basket or on a thin wire. To deposit the above layers, Sn was placed in a basket, Ge was placed in a basket, Pb was placed in a basket, and a Pd wire was wound around a tungsten wire. Evacuate the system and pump continuously until a vacuum of 10 ^{- 6} torr is obtained. In one example of a vacuum system, this takes about 2 hours.

When the aforementioned vacuum is obtained, deposition can begin. First 1000 angstroms of Sn were deposited, then 100 angstroms of Ge, followed by 30 angstroms of Pb. Ge at this stage is in an amorphous form. The substrate was heated to 400K for 30 minutes to change the amorphous Ge into a polycrystalline Ge layer. After forming the polycrystalline Ge layer, 1000 Angstroms of Pb was deposited, where Pd was doped with Ag. To repeat the series, the chamber was opened and reloaded with Sn, Ge, Pb and Pd. The chamber was emptied and the series repeated. Finally, a 1 micron layer of Sn is deposited. Metal conductors are then mounted to the top and bottom of the sheet by conductive epoxy or soldering to make electrical connections.

Figures 6a, 6b and 6c show energy band diagrams for embodiments of different current sources. In each of these embodiments, the top of the conduction band of source 102 is aligned with the top of the conduction band of collector 108 . In the embodiment shown in FIG. 6 a , electrons that have been excited in source 102 tunnel buffer 104 and migrate through filter 106 into empty portions of the conduction band of collector 108 . As shown, the top of the valence band of the filter 106 is below (ie, has a lower energy than) the bottom of the conduction band of the source 102 . In other words, the bottom of the band gap of the filter 106 (semiconductor or insulator) is lower than the bottom of the conduction band of the source 102 . In this way, holes generated in source 102 by excitation of electrons remain in source 102 since there are no energy states in the band gap of filter 106 .

However, in the embodiment shown in Figure 6b, the valence band of the filter 106 extends above the bottom of the conduction band of the source 102, while the bottom of the conduction band is at a higher energy than that of the excited electrons. In this way, the holes in the source 102 tunnel through the buffer 104 and migrate through the filter 106 into the occupied portion of the conduction band of the collector 18, while the excited electrons generated in the source 102 remain in the source 102 because of the filtering There are no energy states in the bandgap of device 106.

In the embodiment shown in FIG. 6 c , electrons that have been excited in source 102 and holes left in localized energy states both tunnel through buffer 104 and migrate through filter 106 . The electrons migrate into the hollow portion of the conduction band of the collector 108 and the holes migrate into the occupied portion of the conduction band of the collector 108 . As can be seen, the bandgap of the filter 106 is small enough that the top of the valence band of the filter 106 is higher than the bottom of the conduction band of the source 102 , and the bottom of the conduction band of the filter 106 is below the energy level of the excited electrons in the source 102 .

Figures 7a, 7b and 7c show energy band diagrams for different current sources and the associated equivalent circuit diagrams and current-voltage diagrams. As shown in Figure 7a, electrons migrate from the source 102 to the hollow part of the conduction band of the collector 108, forming a forward current _I0 . In addition, electrons in the occupied portion of the conduction band of the collector 108 tunnel from the collector 108 through the bandgap of the filter 106 to the collector of the source 102, creating an inverse current _IT . The magnitude of the reverse current _IT is proportional to the voltage across the current source 100, the energy difference between the top of the occupied portion of the conduction band of the collector 108 and the bottom of the conduction band of the filter 106, and varies with the The thickness increases while decreasing exponentially. As shown, since the equivalent circuit diagram of current source 100 looks like an ideal current source with resistor R (resistance of current source 100 ) connected in parallel, the voltage across current source 100 is proportional to resistance R. Thus, while the forward current I ₀ is constant, the reverse current _IT increases linearly with the voltage V ₀ across the current source 100 .

Another mechanism that can cause a reverse current is a current generated by a defect that jumps in the bandgap of the filter 106, as shown in FIG. 7b. That is, if there are defects in the filter 106, eg, due to imperfections in the crystal lattice of the filter 106, and these defects create defect states in the bandgap, a defect current _ID may be generated. Similar to Fig. 7a, the equivalent circuit diagram of the current source 100 in Fig. 7b looks like an ideal current source with a resistor R (resistance of the current source 100) connected in parallel. Thus, while the forward current I ₀ is constant, the reverse current _ID increases linearly with the voltage V ₀ across the current source 100 .

Another mechanism that can cause reverse current flow is the current generated by the internal electric field established in the filter 106 due to the presence of the source 102 and collector 108, as shown in FIG. 7c. That is, when current source 100 is fabricated, the conduction and valence band edges of filter 106 may be clamped at the interface between collector 108 and buffer 104 (if present). This in turn may cause the conduction and valence bands in the filter 106 to bend when the source 102 and collector 108 conduction bands are aligned, creating an internal electric field. In this case, the equivalent circuit diagram of the current source 100 in Fig. 7c looks like an ideal current source with a diode D (resistance of the current source 100) connected in parallel. Since the current in the diode increases exponentially with voltage, similarly, while the forward current I ₀ is constant, the reverse current IDIODE increases linearly with the voltage V ₀ across the current source 100 .

Note that the specification and drawings should be viewed in an illustrative rather than restrictive manner, and all such modifications should be considered to be included within the scope of the present invention. As used herein, the word "comprise" or any variation thereof should be considered to cover an open-ended inclusion relationship whereby a process, method, article or apparatus comprising a list of elements does not include only those elements but may include elements not expressly listed. other elements of or inherent to these processes, methods, articles or equipment.

Accordingly, the foregoing detailed description should be regarded as illustrative rather than restrictive, and it should be understood that the appended claims (including all equivalents) should be regarded as defining the spirit and scope of the invention. Nothing in the above description should be taken as narrowing the scope of the claimed invention and its equivalents.

Claims (40)

1. A current source comprising: a source comprising a metal having a conduction band, a localized energy state at the bottom of the conduction band, and probability amplification; filter, which has a conduction band and is connected to the source, where, the lowest energy level of the conduction band of the metal is less than the lowest energy level of the conduction band of the filter; and A collector is connected to the source via the filter. 2. The current source of claim 1, wherein the metal comprises a disordered metal. 3. The current source of claim 2, wherein the metal comprises a plurality of different metals, wherein atoms of the different metals are arranged in a random manner. 4. The current source of claim 1, wherein the metal comprises a pure transition metal. 5. The current source of claim 1, wherein the metal includes impurities. 6. The current source according to claim 5, wherein, if the metal comprises a non-transition metal, the impurity is an impurity in the same column of the periodic table as the non-transition metal, and if the metal comprises transition metal, the impurity is an impurity in the same column as the transition metal or an impurity in the column to the right of the transition metal. 7. The current source of claim 5, wherein the metal comprises lead and the impurity comprises bismuth. 8. The current source of claim 1, further comprising a magnetic field source that applies a magnetic field perpendicular to the source, the metal having no disorder. 9. The current source of claim 8, further comprising an electric field source that applies an alternating electric field to the source, the electric field being non-parallel to the magnetic field. 10. The current source of claim 9, wherein the electric field source comprises an adjacent layer of the source having a high density of optically active localized phonon modes. 11. The current source of claim 1 , further comprising a buffer between the source and the filter, the buffer comprising at least one of a metal, a semiconductor, or an insulator, wherein the buffer Having a conduction band such that the lowest energy level of the conduction band of the metal of the source is less than the lowest energy level of the conduction band of the buffer. 12. The current source of claim 11, wherein the buffer has a thickness of 10-50 angstroms. 13. The current source of claim 1, further comprising a substrate on which a plurality of structures are formed, each structure including the source, the filter, and the collector. 14. The current source of claim 1, wherein the metal comprises a non-transition metal, the probability amplification can occur within 100 Angstroms of a physical surface of the metal. 15. A current source comprising: a source comprising a metal having a conduction band, a localized energy state at the bottom of the conduction band, and probability amplification; a buffer contacting the source, the buffer having a conduction band and a thickness sufficient to allow charge carriers to pass therethrough, wherein the lowest energy level of the conduction band of the metal is less than the lowest energy level of the conduction band of the buffer; a semiconductor filter contacting the buffer; and collector, which contacts the filter. 16. The current source of claim 15, wherein the metal comprises a disordered metal. 17. The current source of claim 16, wherein the metal comprises a plurality of different metals, wherein atoms of the different metals are arranged in a random manner. 18. The current source of claim 15, wherein the metal comprises a pure transition metal. 19. The current source of claim 15 , wherein the metal includes an impurity such that if the metal includes a non-transition metal, the impurity is an impurity in the same column of the periodic table as the non-transition metal , if the metal includes a transition metal, the impurity is an impurity in the same column as the transition metal or an impurity in a column to the right of the column where the transition metal is located. 20. The current source of claim 15 , further comprising a magnetic field source and an electric field source, the magnetic field source applies a magnetic field perpendicular to the source, the electric field source applies an alternating electric field to the source, the electric field is in relation to The magnetic field is not parallel and the metal has no disorder. 21. The current source of claim 20, wherein said buffer comprises a high density of optically active localized phonon modes, said source of electric field comprising said buffer. 22. The current source of claim 21 , further comprising a substrate on which a plurality of structures are formed, each structure comprising said source, said buffer, said filter, and said collector . 23. A method of forming a current source, the method comprising: depositing a source on a substrate, the source comprising a metal having a conduction band, a localized energy state at the bottom of the conduction band of less than 1000 ppm, and probability amplification; depositing a filter on said source; and A collector is deposited on the filter. 24. The method of claim 23, further comprising depositing a buffer on the source prior to depositing the filter such that the buffer is disposed between the source and the filter, the buffer The device includes at least one of a semiconductor or an insulator. 25. The method of claim 23, wherein the metal comprises a disordered metal. 26. The method of claim 25, wherein the metal comprises a plurality of different metals, wherein atoms of the different metals are arranged in a random manner. 27. The method of claim 23, wherein the metal comprises a pure transition metal. 28. The method of claim 23, wherein the metal includes an impurity, and if the metal is a non-transition metal, the impurity is an impurity in the same column of the periodic table as the non-transition metal, If the metal is a transition metal, the impurity is an impurity in the same column as the transition metal or an impurity in a column to the right of the column in which the transition metal is located. 29. The method of claim 23, further comprising providing a magnetic field source that applies a magnetic field perpendicular to the source, the metal being free of disorder. 30. The method of claim 29, wherein an adjacent layer of the source includes a source of an electric field that applies an alternating electric field to the source, the electric field being non-parallel to the magnetic field, the phase The adjacent layer has a high density of optically active localized phonon modes. 31. The method of claim 23, wherein the metal is a non-transition metal and the probability amplification can occur within 100 Angstroms of a physical surface of the metal. 32. The method of claim 23, wherein the depositing of the source, the filter and the collector is performed under vacuum in a vacuum chamber. 33. The method of claim 23, further comprising depositing a plurality of structures on the substrate, each structure including the source, the filter, and the collector. 34. A device comprising: A current source comprising a plurality of layers including adjacent first and second layers, each of the first and second layers having a conduction band, wherein the first a layer having localized energy states at the bottom of the conduction band and probability amplification, the lowest energy level of the conduction band of the first layer being smaller than the lowest energy level of the conduction band of the second layer ;and load, which is connected to the layer, Wherein the interaction of the layers produces a spontaneous current generated by thermal energy in the current source, causing the current to flow through the load and causing power to be dissipated. 35. The device of claim 34, wherein the first layer of the plurality of layers generating charge from thermal energy comprises a disordered metal. 36. The apparatus of claim 35, wherein the metal comprises a plurality of different metals, wherein atoms of the different metals are arranged in a random manner. 37. The device of claim 34, wherein the first layer of the plurality of layers generating charge from thermal energy comprises a pure transition metal. 38. The device of claim 34, wherein said first layer of said plurality of layers that generate charge from thermal energy comprises a metal that includes an impurity that, if said metal is a non-transition metal, is the same as The non-transition metal is an impurity in the same column of the periodic table, and if the metal is a transition metal, the impurity is an impurity in the same column as the transition metal or to the right of the column in which the transition metal is located column of impurities. 39. The apparatus of claim 34, further comprising a magnetic field source and an electric field source, wherein said first layer of said plurality of layers generating charge from thermal energy comprises a metal without disorder, said magnetic field source applying A magnetic field perpendicular to the first layer, the electric field source applying an alternating electric field to the first layer, the electric field being non-parallel to the magnetic field. 40. The device of claim 39, wherein the second layer of the plurality of layers in contact with the first layer includes a high density of optically active localized phonon modes, and the electric field A source includes said second layer.

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